Chevy cobalt humming

I figure its most likely my belt tensioner bearing but i
just wanted opinions. So this morning i went to
drive my car and i began to hear a loud humming
under acceleration almost like like a light metal on
metal noise coming from the passenger side of the
car, i figured it was a wheel bearing untill i revved
my car in neutral, and too my suprise even when i
was stationary the noise was there when reved